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Sextus Empiricus
An ancient philosopher's criticism of astrology

Bart Koene

This article first appeared in Correlation 15(2), 26-34, Winter 1996/1997. For this version the abstract has been expanded and the notes have been incorporated into the text.

Abstract -- The book Against the Professors written by the Greek physician and philosopher Sextus Empiricus around 200 AD gives many arguments against astrology -- as-above-so-below sympathy does not exist, astrology cannot exist unless all things are destined, forecasting sure events is useless (they cannot be avoided), forecasting unsure events is useless (they can be avoided), why birth and not conception, birth time is uncertain (birth is a long process), birth time cannot be accurately known by the observer of the sky (who might be on a mountain peak), the sky cannot be observed in daytime or on cloudy nights, many people are born at every instant but none was equal to Plato or Alexander the Great, many people with different births nevertheless meet the same end, astrological analogies (Leos are brave like lions) are absurd, astrology is meaningless unless the same planetary positions produce the same result. Many of these arguments are still in use today. Interestingly they cannot be dismissed as the ravings of a practitioner of scientism, reductionism, materialism, or neopositivism, because Sextus was none of these. Instead he practised an early form of skepticism that resolved uncertainties by suspending judgement, a sort of ignorance is bliss. What is the nature of X? All we can know is how it seems. But what is its real nature? Suspend judgement, and thus achieve tranquillity! Nine references.

I am sitting with a philosopher in the garden: he says again and again "I know that that is a tree", pointing to a tree that is near us. Someone else arrives and hears this, and I tell him. "This fellow isn't insane. We are only doing philosophy." Ludwig Wittgenstein 1951

One of the most influential of Western philosophers is the Greek physician Sextus Empiricus, who lived in the 2nd or 3rd century AD. Few things are known about him. We do not even know where he lived or worked. Also, it is uncertain whether he is correctly called "Empiricus." One might get the impression that Sextus is an empiricist, which is not true. The rediscovery and publication of the work of this little-known man in the 16th century influenced such philosophers as Montaigne, Gassendi, Bayle, Descartes, Berkeley, and Hume. The word "scepticism" is often used as a shorthand for "ethical scepticism", "religious scepticism," "scepticism with respect to the paranormal," or some other field of human enterprise. In contrast, Sextus's philosophical scepticism covers all fields where knowledge claims are made. His scepticism is known as pyrrhonism, named after the first known sceptic Pyrrho of Elis (c.365-270 BC).

[Note that the arguments here are not affected by the recent distinction between the Latin-based "scepticism", which has the philosophical sense of doubting everything, and the Greek-based "skepticism" (from skeptikos, to look about, consider, observe), which is used by modern skeptics to emphasise its etymological sense of requiring evidence.]

About Pyrrho the following story is told. When Alexander the Great marched through Asia, the philosopher Anaxarchus of Abdera and his student Pyrrho traveled in Alexander's suite. When somewhere on the route Anaxarchus fell into a swamp, Pyrrho walked by the place were his teacher was in danger of drowning but did not help him out. Fellow travellers had to save Anaxarchus and reproached Pyrrho about that, but Anaxarchus himself praised Pyrrho's indifference and heartlessness.

According to other stories, Pyrrho's friends followed him everywhere to prevent him from falling under a wagon or into an abyss. According to a testimony by his student Timon of Phlius (c.320-230 BC), the goal (telos) of Pyrrho's scepticism is ataraxia: not to bother oneself. No writings of Pyrrho exist, perhaps as a consequence of his philosophy. Fortunately, however, the works of Sextus Empiricus survived the ages. His definition of scepticism in Outlines of Pyrrhonism (PH, translation by Mates 1996) is worth mentioning:

The Skeptic Way is a disposition to oppose phenomena [things perceived] and noumena [things reasoned or assumed] to one other in any way whatever, with the result that owing to the equipollence among the things and statements thus opposed, we are brought first to epoche and then to ataraxia. (PH 1:9)

Sextus explains: "By equipollence we mean equality as regards credibility and the lack of it, that is, no one of the inconsistent statements takes precedence over any other as being more credible."

It is interesting that the word "doubt" does not appear in this oldest-known definition of scepticism. The term does not even appear in the whole account of Sextus on pyrrhonism (ie in Outlines of Pyrrhonism), a fact that has important philosophical consequences. The influential Latin translation by Henri Estienne (Stephanus, 1528-1598) of 1562 wrongly translated the crucial term aporo as dubito. Aporo means "to be at a loss" and does not imply doubt.

Pyrrhonist philosophy is a practical philosophy. Pyrrhonists want to live normally and peacefully, free from metaphysical dogmatism or fanatism. The only form of statement pyrrhonist philosophy accepts is: It seems to me now that P.

Herein P denotes some statement about reality. To give a classical example, a pyrrhonist would not claim that "honey is sweet," but that honey appears sweet to him is something he would usually assent to. Not acceptable in this philosophy is diabebaiousthai ("to maintain firmly, over time and against objections"). Sextus writes:

[The pyrrhonist] follows, without any belief, the ordinary course of life: for this reason he has no pathos [feeling] one way or the other as regards matters of belief, while his pathe [affects] in regard to things forced upon him are moderate. As a human being he has sensory pathe, but since he does not add to these the belief that what he experiences is by nature bad, his pathe are moderate. (PH III:235)

In non-philosophical contexts the pyrrhonist behaves like anybody else. In recent years it has become increasingly evident that Sextus's scepticism (pyrrhonism) is quite different from modem forms of scepticism. Many books on the history of philosophy discuss scepticism only in passing, although it is an important source of philosophy. Nowadays, a new interest in philosophical scepticism is emerging. In 1996 a Dutch translation of all known works of Sextus appeared, and recently I reviewed a collection of articles about the history and forms of philosophical scepticism (Koene 1997, De Martelaere 1996). Also a new translation of the Outlines of Pyrrhonism by Benson Mates appeared, two years after the translation by Annas and Barnes (Sextus 1994). The former has an elaborate introduction and commentary.

Below, special attention will be paid to Sextus's description and criticism of astrology in Against the Astrologers, which is a part of his book Against the Professors (here abbreviated as ATP), that comes in six parts. For citations I have used the formal and accurate translation by R.G.Bury. In this book also the grammarians, rhetoricians, geometers, arithmeticians, and musicians are criticised. A discussion of these other parts is beyond the scope of this article. I mention them only to illustrate that Sextus's philosophy is a total and not a partial scepticism.

Against the astrologers
In Against the Astrologers, Part V of Against the Professors, Sextus inquires into astrology or the Mathematical Art, which is distinguished from the Complete Art (arithmetic and geometry), and from astronomy. The Greek text is only 24 pages in the Loeb Edition. Evidently, Sextus has no high opinion of astrology (in the following quote he uses the word "Chaldeans" -- people from Mesopotamia -- as almost synonymous with "astrologers"):

[Astrology] is rather the casting of nativities, which the Chaldeans adorn with more high-sounding titles, describing themselves as "mathematicians" and "astrologers," treating ordinary folk with insolence in various ways, building a great bulwark of superstition against us, and allowing us to do nothing according to right reason. This we shall understand after we have first traced back a little the things which contribute to their method of speculation. (ATP V:2-3)

Next he summarises the astrology of his time. Of course, Sextus focuses on points necessary for his arguments against astrology. However, his description seems accurate enough to give a good impression of astrology as it was practised in the 2nd or 3rd century AD. Therefore, his text may also be useful for historical research into astrology. Where it seems the best thing to do, I give a summary or description of the essenxe of his text.

Sextus's description of astrology
The basic assumption of astrology is that "things on earth 'sympathize' with those in the heavens, and that the former are always newly affected by the effluences of the latter." (ATP V:4) This may be a possible opinion of a modern astrologer, but the majority of astrologers think differently. Because of this assumption, the astrologers "declare that the seven stars [Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn] stand in the relation of efficient causes for the bringing about of everything which occurs in life, and that with them the parts of the zodiac co-operate." (ATP V:5)

As modern astrologers do, they divide the zodiac into twelve signs, and each sign into 30 degrees and each degree into 60 lepta ("minutes"). The signs are masculine or feminine, bi-corporal (Pisces and Gemini) or not (the others), and some are tropical (Aries, Libra, Capricorn, Cancer) and others fixed (Taurus, Scorpio, Leo, Aquarius):

Masculine and feminine are those which possess a nature which aids the birth of males and females: thus the Ram is a masculine Sign, but the Bull, they say, is feminine, the Twins masculine and the rest alternate in a similar proportion, some masculine, others feminine. (ATP V:7)

Some astrologers use a generalisation of this structure:

Some, too, divide each Sign into twelve parts and use much the same method: as, for instance, in the case of the Ram, the first twelfth part of it they describe as the Ram and male, the second as the Bull and female, the third as the Twins and male: and the same rule holds for the other portions. (ATP V:8)

The signs in astrology have not changed over the past 18 centuries. Also unchanged is the importance of Ascendant, MC, Descendant, and IC for the horoscope:

However, of all these Signs those which are dominant at each geniture for the production of effective influences and from which they principally frame their prognostications are, they say, four in number; and to these they give the generic name of centres, and more specifically they call them horoscope [ascendant], mid-heaven [MC], setting [descendant], subterranean and anti-midheaven [lC]. (ATP V:12)

Sextus also sketches the astrological meaning of the various houses, though the word "house" is not mentioned in these sections (he does so when he speaks about the planets). The angular houses have the names already given above. The other houses have names such as goddess [3rd], good fortune [5th], punishment [6th]. principle of death [8th],god [9th], and evil daemon [12th]. He also reports the astrological theory that connects parts of the human body to planets and signs:

And there have been some Chaldeans who have referred each part of the human body to one of the Signs as 'sympathizing' therewith: thus they call the head the Ram, the neck the Bull, the shoulders the Twins, the breast the Crab, the sides the Lion, the buttocks the Virgin, the flanks the Scales, the pudenda and womb the Scorpion, the thighs the Archer, the knees Capricorn, the shins Aquarius, the feet the Fishes. (ATP V:21)

The Chaldeans watched the rising sign by night by sitting on a high peak observing the stars after being informed of the birth by the sound of a gong. During the day, however, they studied the horologes (sundials) and the motions of the sun. The Sun and Moon are the most important of the "seven stars":

and for this reason the Egyptians liken the Sun to the king and the right eye, and the Moon to the queen and the left eye and the five stars to lictors and the other fixed stars to the rest of the people. (ATP V:31)

These "five stars" are beneficent (Jupiter and Venus), maleficent (Mars and Saturn) or common (Mercury). Some astrologers, however, believed that the position of the planets influenced their effect:

They say also that the same stars have increased power owing to their being in their proper houses or elevations or boundaries, or owing to the fact that some are guarded by others or because they look towards one another or are in a certain configuration one with another, or because they are at the centres [ie ascendant, MC, descendant or IC]. (ATP V:33)

Hereafter, Sextus sums up the rulerships of the different planets: "the Lion is the house of the Sun, the Crab of the Moon," and so on. Next he discusses the meaning of the "elevation" of a planet in contrast to "depression" (where a planet has little power) and the meaning of a "triangular figure" and "quadrangular figure."

Most of this will probably sound familiar to modern astrologers, even though they tend to consider the sun sign as the most important factor in the horoscope, whereas eighteen centuries ago it was the ascendant. Nevertheless, eighteen centuries have not affected much of the basic concepts of astrology. Further differences between the astrology in Sextus's time and today are beyond the scope of this article. I have only indicated what is apparent from the account of the pyrrhonist.

Sextus's criticism of astrology
Sextus begins with three arguments against astrology, which were more common in his time. First, he argues forthrightly that terrestrial things do not "sympathize'' with things celestial. Then an argument about destiny: for unless all things happen according to destiny, astrology, which maintains this, does not exist" (ATP V:45). His third argument is the following. There are three possibilities for events: they occur by necessity, by chance, or by our own action. With respect to chance events, one may argue that this is impossible, because they are irregular, and for things that occur through our own action and have "no predetermined cause,'' no one can possibly make a prediction. More eloquent is the argument in the case of necessity:

But if they do so about necessary events, their forecasts are useless in practice: for it is impossible to avert what happens by necessity, for that must take effect whether we like it or dislike it. And the prophecy would have been useful only if it had had reference to the means of averting it. (ATP V:47)

Evidently, not much knowledge of astrology is required to invent the arguments above. Sextus calls them "long range fire" and he adopts a "method of attack at close quarters" (ATP V:49). His first argument can be summarized in the form of the question: Why is the time of birth used and not the time of depositing of the seed or the conception? A number of problems to determine the latter are mentioned showing Sextus' medical expertise. The time of birth is another problem:

For ... the moment when birth should be said to take place is a matter of doubt, is it when the child begins to emerge into the cold air, or when it has emerged a little, or when it is deposited on the ground? (ATP V:65)

The determination of the ascendant is the key to the horoscope. If it is wrong or impossible, astrologers have no basis for their work. Nowadays, it is relatively easy to acquire the necessary astronomical data when the time of birth is known accurately. Against the possibility of synchronisation of birth and observation of the stars, Sextus forwards the following argument:

Next, let it be granted that the time of birth is discoverable, still it is not possible to transmit it by sign at the exact time. For the fact that in moving up to the peak [where the observer is] the sound of the gong takes a considerable amount of time. ... And what is observed in the case of those who fell trees on a mountainside is a proof of this: for the sound of the blow is heard a considerable time after the fall of the axe, so that it takes some time to reach the listener. (ATP V:60)

Determination of the horoscope for children born in daytime was, of course, rather problematic. At night, on the other hand, cloudiness, mist, or even poor vision on the part of the observer could easily spoil adequate observation of celestial phenomena. These were serious limitations for astronomy and astrology. With respect to people consulting the Chaldeans, Sextus adds:

yet it is plain that none of the ordinary persons who apply to the Chaldeans has observed for himself the exact time before applying: for the task calls for much expertness, as we have shown above, and seems beyond the capacity of the ordinary man. (ATP V:86)

Next Sextus lets the problem of birth time rest and discusses some consequences of astrology. Cases of people being born simultaneously, at different times and people with a similar fate are discussed. Further, he compares the lives of a man and an animal. The following applies to people born (approximately) simultaneously:

some, for example, have been kings while others have grown old in chains. Thus, though many throughout the world were born at the same time as he, none was equal to Alexander of Macedon [Alexander the Great 356-323 BC] nor to the philosopher Plato. (ATP V:89)

When people are born at different times it does not imply that they will be absolutely different:

For if those who have the same "disposition'' at birth meet with the same results during life, then certainly those whose births are different become different. But this is false; for we see many, who differ as to age and bodily shape and countless other peculiar affections, yet meeting with a similar end. (ATP V:91)

Of different people that have a similar fate Sextus gives the following examples:

For the man who was born in the arrow's point of the Archer is doomed -- according to astrological theory -- to be slain, how is it that all those myriads of barbarians who fought against the Greeks at Marathon were all slain at one time? For the horoscope was not the same for them all. And again, if he who was born in the pitcher of Aquarius is doomed to suffer shipwreck, how is it that the Greeks who were being brought back from Troy were all drowned together round the Hollows of Euboea? For that all these men, who differed greatly from another, could have been born in the pitcher of Aquarius is impossible. (ATP V:92-93)

Another argument compares the lives of a man and an animal born simultaneously:

And some other person will raise the doubt regarding the irrational animals. For if the effects in life naturally result from the configurations of the stars, then, when a pack-ass and a man are both born in this same portion of the Sign, the same kind of life ought to have followed as a result in both cases, instead of the man being, for example, conspicuous as a statesman and admired by the citizens, while the pack-ass is continually laden with burdens or led away to the mill-houses. (ATP V:94)

Sextus concludes from these arguments that it is not reasonable or logically understandable that life is ordered according to the motions of the stars. But this is not the end of his argumentation. Already in the first centuries of our era, astrologers associated shapes and characters of men with the figures of the signs. This practice is attacked by Sextus:

For, in the first place, if they assert that the man born in Leo is brave because the lion is a valiant and manly beast, how is it that they reckon the Bull, which is on a par with the Lion to be a womanish beast? And secondly, it is nonsense to suppose that the lion in the heavens, that most beautiful Sign, bears any analogy to the earthly lion: for it is probable that the ancients gave them names of this sort merely because of the similarity of their figures, and perhaps not even for this reason, but just for the sake of clearness in exposition. (ATP V:96-97)

The following argument refutes some properties that were associated with the sign Virgo:

And again if he who has the Virgin for horoscope [ie ascending] is straight-haired, bright-eyed, and white-skinned, it must follow that none of the Ethiopians has the Virgin for horoscope, else they will be granting that an Ethiopian is white, bright-eyed and straight-haired, which of all things is the most absurd. (ATP V:102)

The final argument that I will show here is fascinating, because of Sextus's request for reproducibility as evidence:

I affirm that if the prediction is to be reliable, the same position of the stars ought not be observed once only in connexion with the life of some one person, but a second time with a second life, and a third one with a third, so that from the equality of the resultant effects in all the cases we might learn that when the stars have assumed a certain configuration the result will certainly be of one particular kind. (ATP V:103) (my emphasis)

Much of Sextus's criticism of astrology seems rather modern. Many of his arguments can be and are still used by modern sceptics of astrology. Further, the book of Sextus clearly illustrates that one does not have to be an adherent of scientism, reductionism, materialism or (neo) positivism -- just a few of the terms some astrologers use as invectives -- to object to astrology. For pyrrhonists are none of these. Now I will discuss Sextus's arguments in the light of his sceptical philosophy.

One may wonder why Sextus's statements on astrology are not of the form "lt seems to me now that P." First, I respond like a pyrrhonist would. Sextus was simply reporting as a chronicler what appeared to him to be the case at the time that he wrote it (PH I:4). Sextus followed his feelings (pathe) with respect to astrology (see PH III: 235, quoted above). Sextus also uses statements of the form P, for which the true philosophical meaning is "It seems to me now that P." He emphasises this frequently in his Outlines of Pyrrhonism.

By speaking this way, pyrrhonists are not always distinguishible from ordinary people and their philosophical opponents, the Dogmatists (mainly Stoics, Epicureans and Academics). In the eyes of Sextus, dogmatism is something like a disease that needs treatment (PH III:280). He hopes that no matter how good or bad his arguments are dogmatists will be cured of their dogmatism.

In the literature, there is a lively discussion about philosophical scepticism (eg Mates 1992, De Martelaere 1996). Being less vulnerable to attempts of refutations than several other forms of scepticism, including many modern forms of scepticism, pyrrhonism appears to be a tough nut to crack. In Doubt and Dogmatism, Burnyeat (1980:50) writes about the pyrrhonist appearance-statement (ie it seems to me now that P): "At times, no doubt, the non-epistemic reading is sheer bluff on Sextus's part, but the objectors opposition will itself be no better than bare counter-assertion unless he can muster more to say" (my emphasis).

I do not think Burnyeat is right. As said, pyrrhonists sometimes use statements of the form "P" as an abbreviated way of saying "lt seems to me now that P." When asked about it later, however, in pyrrhonist philosophy one is free to say whether "P" seems to be the case at that moment. Hence, to appearances they seem to adhere undogmatically. According to Sextus, moderation is a property of their philosophy (PH I:15, I:29, III:135). It should be added that pyrrhonists are not conspicuous and are hard to distinguish from other people in daily life.

With respect to Sextus and, in passing, Ludwig Wittgenstein, Cohen (1984:419) remarks: "Neither could repress completely his philosophical, dogmatic temperament" (my emphasis). Here the term "dogmatic" seems rather out of place to me. (Also, in passing, what psychological method did Cohen use to determine that Sextus Empiricus and Ludwig Wittgenstein "repressed" their temperaments?) So what is the matter? In the introduction of his article he writes that he hopes to "enrich us with some new, perhaps even provocative, insight into the psychology of doubt and certainty, and even into the nature of the philosophical mentality as a whole" (Cophen 1984:406). On page 423 footnote 14 Cohen also quotes the sentence of Burnyeat that I quoted from Doubt and Dogmatism (remarkably without the second part of the sentence that I emphasised); however, he refers to this work as Doubt and Scepticism, ie he replaced "dogmatism" by "scepticism". Perhaps that's what must be done with his strange psychological remark. Thus it should read: "Neither could repress completely his philosophical, sceptic temperament."

Of course, pyrrhonism raises questions. Sextus's definition of scepticism (PH 1:9) may be represented by the following scheme: isostheneia (equal strength (of arguments)) leads to epoche (suspension of judgement) leads to ataraxia (mental tranquillity). Suspension of judgement (epoche) is the means, and tranquillity (ataraxia) is the goal, of his philosophy. One of the central questions seems to me: How can one always find (counter) arguments with equal strength? In the case of the philosophies of his so-called dogmatic opponents, Sextus often gives useful examples.

Sextus's arguments Against the Astrologers is not typical of a pyrrhonist and could also have been written by any other author of his time. To me it seems that Sextus differs from other philosophers in the way he criticises astrologers, though he still considers them -- I think -- as a species of dogmatists. He does not mention the words isostheneia and epoche in connection with astrological theory. It is apparent that astrology is weighed against "common sense" or reason (logos). For pyrrhonism -- like stoicism and epicurism, a "practical wisdom philosophy" -- it seems important that things are plausible.

Much of Sextus's criticism of astrology may seem rather definitive. I do not think though that Sextus was dogmatic in his statements about astrology. For he would state otherwise when someone would convince him of the contrary. Nevertheless, I do not have the impression that the most capable modern defender of astrology would be able to provide the necessary evidence that a pyrrhonist would accept. This of course remains to be seen.

My thanks go to Joanna Ashmun for her constructive criticism and helping me polish my English.


Burnyeat M (1980). Can the Sceptic Live His Scepticism? In Doubt and Dogmatism Eds. M Schofield, M Burnyeat and J Barnes, Oxford: Clarendon Press, pp. 20-53.

Bury RG (1933-1949). Sextus Empiricus. 4 Vols. Loeb Classical Library. London: Heinemann.

Cohen A (1984). Sextus Empiricus: Scepticism as a Therapy, Philosophical Forum 15, 405-424.

De Martelaere P (Ed) (1996). Het Dubieuze Denken: Geschiedenis en Vormen van Wijsgerig Scepticisme [Doubtful Thinking: History and Forms of Philosophical Scepticism]. Kampen: Kok Agora, The Netherlands.

Koene B (1997). Het Dubieuze Denken [Doubtful Thinking], Skepter, 10(1) (book review).

Mates B (1992). Pyrrhonism and Modem Skepticism. In Philosophie, Psychoanalyse, Emigration. Eds P Muhr, P Feyerabend, and C Wegeler, Wien: WUV-Universitdtsverlag, pages 210-227.

Mates B (Ed) (1996). The Skeptic Way: Sextus Empiricus's Outlines of Pyrrhonism. Oxford University Press.

Sextus Empiricus (1996). Grondslagen van het scepticisme [Foundations of Scepticism]. Translated by R Ferwerda. Baarn: Ambo, The Netherlands.

Sextus Empiricus (1994). Outlines of Scepticism (Translated by J Annas and J Barnes). Cambridge University Press. ~b

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